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A person whose far-point is at 30cm want...

A person whose far-point is at `30cm` wants to read at `50cm`. The power of the lens should be

A

`-1.0D`

B

`-1.33 D`

C

`-1.62 D`

D

`-2.0 D`

Text Solution

Verified by Experts

The correct Answer is:
B
`(1)/(-(F.P.)) - (1)/(-("distance of object")) = (1)/(f)`
`(1)/(-30) - (1)/(-50) = (-5+3)/(150) = (1)/(f) rArr f= -75cm`
`P = (100)/(f(cm)) = (100)/(-75) =- (4)/(3)=-1.33D`
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CP SINGH-OPTICAL INSTRUMENTS-EXERCISES
  1. 1. Identify the wrong description of the above figures

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  2. Mark the correct options (i) If the far point goes ahead, the power ...

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  3. In the case of hypermetropia (i) the image of a near object is forme...

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  4. Astigmatism for a human eye can be removed by using

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  5. A man, wearing glasses of power +2D can read clearly a book placed at ...

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  6. A person whose far-point is at 30cm wants to read at 50cm. The power o...

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  7. A person wears glasses of power -2.5D. The defect of the eye and the f...

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  8. A far-sighted man can see clearly at a distance of 1.0m. The power of ...

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  9. The near point of a person is 50 cm and the far point is 1.5m. The spe...

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  10. An eye specialist prescribes spectacles having combination of convex l...

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  11. How should people wearing spectacles work with a microscope

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  12. Chromatic aberrations in the formation of image by a lens arise becaus...

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  13. Which of the following quantities related to a lens depend on the wave...

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  14. Let f(v) and f(r) are the focal lengths of a convex lens for violet an...

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  15. An achromaic convergent system of focal length +20cm is made of two le...

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  16. A combination of two thin lenses of the same material with focal lengt...

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  17. The dispersive powers of crown and flint glasses are 0.02 and 0.04 res...

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  18. The dispersive power of the material of lens of focal length 20cm is 0...

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  19. Spherical aberration in a thin lens can be reduced by

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  20. Spherical aberration in a lens

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